The present invention relates to composite structures suitable for absorbing discharged body fluids. Such structures can be incorporated into disposable absorbent articles such as sanitary napkins, infant diapers, adult incontinence pads and the like.
Absorbent structures which comprise entangled masses of fibers, i.e., fibrous webs, are well known in the art. Such structures can imbibe liquids, such as discharged body fluids, both by an absorption mechanism wherein fluid is taken up by the fiber material itself and by a wicking mechanism wherein fluid is acquired by, distributed through and stored in the capillary interstices between fibers. One means for increasing the absorbent capacity of such fibrous web structures is to incorporate therein so-called superabsorbent polymers which imbibe fluid to thereby form a swollen hydrogel material. The resulting hydrogel serves to retain fluid within the structure. An absorbent structure of this type wherein hydrogel-forming materials in particulate (including fiber) form are incorporated into fibrous webs is disclosed in Weisman and Goldman; U.S. Pat. No. 4,610,678; Issued Sept. 9, 1986.
While absorbent capacity is a significant factor in determining the suitability of absorbent structures for use in disposable absorbent articles, other factors can also be important. For disposable absorbent articles which are worn or positioned in a particular relationship to the user's body, physical properties of the absorbent structures utilized in such articles are likewise relevant considerations. Thus features such as flexibility; resilience, e.g., resistance to bunching; softness; and tear resistance must generally be taken into account when selecting appropriate types of absorbent structures for use in absorbent articles. Absorbent structure properties which determine the comfort of the absorbent articles incorporating such structures are especially important in products like sanitary napkins wherein the intimate contact of the article with the wearer's body make the comfort properties of such structures especially noticeable.
One way of imparting strength and flexibility to fibrous web absorbent structures has involved the use of blown microfibers in combination with staple absorbent fibers to fashion absorbent products. Anderson et al, U.S. Pat. No. 4,100,324; Issued July 11, 1978, for example, discloses preparation of absorbent "fabrics" fashioned from blown microfibers and wood pulp fibers. Technology has also been developed to enhance the absorbent capacity of microfiber/stable fiber webs by incorporating therein particles of fluid-absorbent polymeric material. For example, Kimberly-Clark Ltd., British Patent Spec. No. 2,113,731A, Published Aug. 10, 1983; Kolpin/Brownlee, U.S. Pat. No. 4,429,001, Issued Jan. 31, 1984 and Minnesota Mining & Manufacturing Company, European Patent Application EP-A-156649, Published Oct. 2, 1985 all disclose sorbent sheet materials which comprise webs of entangled blown microfibers, generally absorbent staple fibers and particles of solid, high-sorbency, liquid-sorbent polymer materials.
Notwithstanding the existence of such microfiber-based prior art absorbent structures, there is a continuing need to identify additional absorbent structures which contain microfibers and staple fibers in order to provide strength, integrity and resilience and which also contain liquid-sorbing polymeric material in order to provide absorbent capacity. There is also a need to identify structures of this type which especially desirable comfort properties. Accordingly, it is an object of the present invention to provide improved absorbent structures comprising certain types of blown microfibers, staple fibers and liquidsorbing polymeric material.
It is a further object of the present invention to provide absorbent structures which have acceptably high absorbent capacity but which are also exceptionally resistant to tearing and bunching, and which are especially flexible and resilient.
It is a further object of the present invention to provide disposable absorbent articles such as sanitary napkins, diapers, training pants, incontinence pads and the like which utilize such improved absorbent structures to form their absorbent cores.